CORE B: The purpose of this core is to establish and administer a prospective cohort, clinical database, and biospecimen repository that will enable research on the role of RSV in atopic and chronic lung disease inception. The core will support scientific projects that focus on host factors (Project 1), viral factors (Project 2), and mechanisms through which target interventions may work (Project 3). This core will prospectively enroll and follow 2000 term otherwise healthy infants who will be < 6 months of age during winter virus season through age 3-4 years, at which time recurrent childhood wheeze and allergic sensitization will be defined - named the ReSPIRA cohort (Respiratory Study for Protection of Infants from RSV to Asthma). The core will provide detailed clinical information and biospecimens on a tightly phenotyped group of infants with a high likelihood of developing asthma, and thus allows the projects which this core serves to identify host genetic, viral genetic, cellular, immune, and molecular determinants of recurrent wheezing, early childhood asthma and atopy following infant RSV infection. The first two years of the clinical core will focus on enrollment, and the 3 subsequent years will focus on cohort follow-up and delivery of data and biospecimens to co-investigators, whose projects will address research questions related to RSV illness and early childhood asthma. Our specific aims are to: (1) Create the ReSPIRA cohort; (2) Clinically characterize (phenotype) the infant cohort in Argentina with regards to RSV infection status, host response, and lung injury during infancy, on the outcomes of recurrent childhood wheezing, asthma, and atopy; and (3) Establish and maintain a biospecimen repository and distribute its' resources to conduct studies on the mechanisms through which RSV infection may lead to recurrent wheezing and asthma development. This core supports the overall Center by centralizing resources on cohort inception, detailed classification of RSV infection/exposure, outcomes assessments, data management and administration, to support the study of the role of infant RSV illness on later childhood atopy and asthma outcomes. As bronchiolitis and asthma are the most common, serious, acute and chronic conditions of infancy and childhood, respectively, and are diseases that disproportionately burden vulnerable populations, this core and supported projects will have major, long-lasting impact by improving our understanding of the role of, and the mechanisms through which RSV contributes to later childhood outcomes.